Preparation method of high-flux high-efficiency catalytic ceramic membrane

Abstract

The application discloses a preparation method of high-flux high-efficiency catalytic ceramic membranes and belongs to the technical field of functional ceramic membrane preparation. Cobalt-doped Prussian blue analogue powder and aluminum oxide powder are mixed in proportion, and then dry pressing is adopted to prepare a dry blank; the dry blank is sintered at 950 DEG C for 5.5-6.5 hours under an air atmosphere, and the high-flux high-efficiency catalytic ceramic membrane is obtained. The ceramic membrane prepared by the in-situ sintering method can maintain the strength of the aluminum oxide support body and improve the water permeability of the aluminum oxide support body, has the characteristics of promoting the activated oxidative degradation of organic pollutants in water by peroxymonosulfate, and can be applied to the field of water treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional ceramic membrane preparation, and specifically relates to a method for preparing a high-throughput and high-efficiency catalytic ceramic membrane for in-situ degradation of organic pollutants. The method combines ceramic membrane filtration with AOP technology to achieve high-throughput and high-efficiency in-situ degradation of organic pollutants on the membrane surface. Background Art

[0002] In recent years, deep water pollution treatment technology based on peroxymonosulfate (PMS) activation and oxidation of organic pollutants has attracted much attention. Traditional PMS activation methods mainly include using transition metal ions, metal oxides, UV, ultrasound and other methods to break the peroxy bond of PMS to produce sulfate radicals (SO4· − ) and hydroxyl radicals (HO•), thereby achieving degradation and mineralization of organic pollutants. However, the energy consumption of activated PMS technology is highly correlated with the dosage of the oxidant and catalyst. Metal catalysts have low catalytic efficiency, and the metal catalyst and metal oxides need to be separated from the treated water. These factors significantly impact process efficiency. Therefore, there is an urgent need to develop highly efficient catalysts to achieve efficient wastewater treatment, degrade organic pollutants, and quickly separate the treated water from the catalyst.

[0003] Ceramic membranes are solid membrane materials used in membrane separation technology. Due to their advantages, such as high-temperature and chemical resistance, insensitivity to bioerosion, low maintenance costs, high mechanical strength, long service life, and easy assembly of flat-plate modules, they have experienced rapid development over the past half century and are widely used in fields such as petrochemicals, pharmaceuticals, electronics, metallurgy, food, and environmental protection. Ceramic membranes are corrosion-resistant and easily separate from the treated water. Furthermore, their porous surface structure makes them an excellent catalyst support. Previously, catalysts were often attached to the membrane surface through impregnation, but this method suffers from unstable catalyst loading and is easily washed away by hydraulic pressure or carried away from the membrane surface by macromolecules during the wastewater treatment process. In-situ sintering, on the other hand, offers a more stable structure, distributing the catalyst both on the membrane surface and within the membrane after sintering. Compared to membranes loaded with catalysts through impregnation, membranes produced using this method are less susceptible to catalyst loss and have a significantly longer service life. Activating the catalyst by attaching PMS to ceramic membranes not only effectively improves the efficiency of the catalytic process but also promotes the sustainable development of water treatment technology. This combination of technologies is expected to play an important role in solving current problems in the degradation of organic pollutants and provide new solutions for the efficient use and sustainable development of global water resources. Summary of the Invention

[0004] In order to solve the above problems, the present invention aims to provide a method for preparing a high-throughput and high-efficiency catalytic ceramic membrane. The prepared ceramic membrane can achieve high-throughput and high-efficiency in-situ degradation of organic pollutants.

[0005] The technical solution adopted in the present invention is as follows:

[0006] A method for preparing a high-throughput and high-efficiency catalytic ceramic membrane comprises the following steps:

[0007] (1) Prussian blue (PBA) and Al2O3 were mixed uniformly in proportion by ball milling. The particle size of PBA and Al2O3 was 100-200 nm. The mixture was then pressed for 3-7 minutes using a mold with a diameter of 30 mm and a hydraulic press at a pressure of 10-30 kPa to obtain a dry blank of the membrane with a thickness ranging from 2-4 mm.

[0008] (2) The product is then sintered in an air atmosphere at a high temperature using a muffle furnace for 5.5 to 6.5 hours, with a heating rate of 5°C per minute.

[0009] As one of the preferred technical solutions for the preparation method of the above-mentioned high-flux and high-efficiency catalytic ceramic membrane, the Prussian blue-like material is prepared by the following method: 1.20-3.00 g of potassium ferrocyanide powder and 1.5-2.5 g of cobalt chloride powder are dissolved in 50-200 ml of water at 25°C, stirred continuously for 24 hours, and centrifuged and dried to obtain a Prussian blue-like material (PBA).

[0010] As one of the preferred technical solutions for the preparation method of the above-mentioned high-flux and high-efficiency catalytic ceramic membrane, the mass ratio of PBA to Al2O3 is 1:3~5, preferably 1:4~5, and more preferably 1:4.

[0011] As one of the preferred technical solutions for the preparation method of the above-mentioned high-flux and high-efficiency catalytic ceramic membrane, the temperature of the high-temperature sintering is 950~1100°C, preferably 950~1000°C, and more preferably 950°C.

[0012] The present invention also provides a ceramic membrane prepared by the above method. After preparing the catalytic ceramic membrane, the water permeability of the prepared ceramic membrane is tested in a membrane filtration reactor. The prepared membrane is then used to activate peroxymonosulfate in an edible brilliant blue solution, and the catalytic performance of the membrane is tested to demonstrate the membrane's good performance, thereby achieving a good combination of ceramic membrane and PMS technology for high-throughput and efficient in-situ degradation of organic pollutants in water.

[0013] Therefore, the high-flux and high-efficiency catalytic ceramic membrane prepared by the present invention can be used in the field of water treatment.

[0014] The present invention adopts an in-situ sintering method to dope the catalytic material into the ceramic support, thus obtaining an integrated high-throughput and high-efficiency catalytic ceramic membrane. Compared with the existing technology, the present invention has the following outstanding features and outstanding improvements:

[0015] 1. Prussian blue-like materials are added to the prepared catalytic ceramic membrane. After firing, the membrane has a good porous structure and the active sites of the catalyst are evenly distributed on the membrane surface and in the membrane pores.

[0016] 2. During the sintering process, the combination of Prussian blue and alumina can increase the porosity of the ceramic membrane, significantly improving its membrane flux compared to traditional alumina membrane.

[0017] 3. Compared with the impregnation loading method, in addition to the membrane surface, catalytic active sites are still distributed inside the membrane, which has higher catalytic efficiency and thus exhibits higher catalytic activity. The catalyst of the in-situ sintered membrane is not easy to lose, and the in-situ catalytic degradation of pollutants can be achieved during the filtration process, and the service life of the membrane is relatively longer.

[0018] 4. The co-sintering process of Prussian blue and alumina can effectively reduce the sintering temperature of alumina, so that it can be successfully sintered within 1000°C, thereby reducing the sintering cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the process flow chart for preparing catalytic ceramic membranes.

[0020] Figure 2 This is the SEM image of the catalytic ceramic membrane.

[0021] Figure 3 The catalytic performance of catalytic ceramic membrane in peroxymonosulfate solution. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0023] As attached Figure 1 As shown, the catalytic ceramic membrane prepared by the present invention is prepared by dry pressing and sintering method. The specific process is: Prussian blue-like powder and alumina are mixed in proportion, dry pressed into shape, and then calcined at high temperature in a muffle furnace. The calcination temperature is 950°C, the holding time is 6h, and the heating rate is 5°C / min.

[0024] The alumina is boehmite with the molecular formula of γ-AlOOH (hydrated alumina), and comes from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0025] The Prussian blue-like powder was prepared in the laboratory. The specific preparation method is as follows: 1.85g of potassium ferrocyanide powder and 2g of cobalt chloride powder are weighed and dissolved in 100ml of water. After continuous stirring at room temperature for 24 hours, centrifugation is performed, and then drying is carried out in a vacuum environment at 60°C. Finally, the powder is crushed in a mortar to obtain a Prussian blue-like powder (PBA).

[0026] The potassium ferrocyanide was purchased from Hubei Yunmei Technology Co., Ltd.

[0027] The cobalt chloride was purchased from Shanghai Jizhi Biochemical Technology Co., Ltd.

[0028] Biaxial flexural strength (BFS) and compressive strength (CS) tests are used to comprehensively assess the brittleness, toughness, and overall strength of the prepared catalytic ceramic membrane. A higher BFS indicates that the ceramic membrane can withstand significant bending forces without breaking, while the CS test reflects the ceramic membrane's ability to withstand pressure in actual applications. Example 1

[0029] 0.4g of Prussian blue-like powder and 1.6g of aluminum oxide were mixed in a 1:4 ratio. The particle sizes of the Prussian blue-like powder and aluminum oxide were 100-200nm. The mixture was then pressed using a 30mm diameter mold and a hydraulic press at 18 kPa for 5 minutes to produce a dry film with a thickness of 3mm. The film was then sintered in an air atmosphere at 950°C in a muffle furnace for 6 hours, with a heating rate of 5°C / minute. Example 2

[0030] The difference between this embodiment and the first embodiment is that 0.5 g of Prussian blue-like powder and 1.5 g of aluminum oxide are mixed evenly, and other operations are the same as those in the first embodiment. Example 3

[0031] The difference between this embodiment and the first embodiment is that the sintering temperature of the muffle furnace is 1100° C., and other operations are the same as those of the first embodiment.

[0032] Comparative Example 1

[0033] When the film forming conditions are the same as those in Example 1, the sintering conditions are changed to firing in a tube furnace under an argon atmosphere, and the other firing conditions are also the same as those in Example 1.

[0034] Comparative Example 2

[0035] No Prussian blue-like powder was added, and only 2.0 g of alumina was weighed for firing. To ensure successful sintering of the membrane, the sintering temperature was 1400° C. The other membrane preparation and firing conditions were the same as those in Example 1.

[0036] The ceramic membranes prepared in the above examples and comparative examples were tested for biaxial flexural strength (BFS) and compressive strength (CS) (results shown in Table 1). The BFS and CS of the membrane prepared in Example 1 were 18 MPa and 46.5 MPa, respectively, which were significantly higher than the standard (I > 30 MPa) according to GB / T4100-2006, and thus the membrane belonged to the first-class building material. Therefore, the ceramic membrane prepared in Example 1 could well withstand high-pressure filtration. In Example 2, the high content of Prussian blue analog added as the main matrix material of the ceramic membrane resulted in a decrease in the content of alumina, thereby greatly reducing the strength of the sintered membrane. Due to the addition of excessive Prussian blue analog, the microstructure of the ceramic membrane was unevenly changed, the internal defects were increased, and thus the BFS and CS were decreased, and the membrane was prone to brittle fracture. In Example 3, the increase in temperature promoted more sufficient reaction between alumina and Prussian blue analog, thereby increasing the density of the ceramic membrane, reducing the porosity, and making the microstructure of the membrane more uniform and dense. In summary, a higher sintering temperature helps to reduce the porosity and defects and improve the overall mechanical properties of the ceramic membrane. In Comparative Example 1, due to the oxidation of the Prussian blue analog, the ceramic membrane formed iron oxide phase, increased the porosity and defects, and reduced the density of the membrane, thereby reducing the BFS and CS of the membrane. The membrane using only alumina will not undergo oxidation reaction during sintering, and the densification process of alumina is usually smooth, which can form a uniform microstructure, reduce the porosity, and thus enhance the mechanical properties of the material.

[0037] Table 1: Strength performance of the membrane

[0038] Examples Biaxial bending strength (MPa) Compressive strength (MPa) Example 1 18.0 46.5 Example 2 9.8 24.3 Example 3 29.8 55.3 Comparative Example 1 51.3 62.9 Comparative Example 2 70.5 90.7

[0039] The sintering of conventional alumina ceramic membranes is usually carried out at a temperature of 1100°C or higher. It has been determined by experiments that the co-sintering of Prussian blue analog and alumina can effectively reduce the sintering temperature of alumina. At a relatively low calcination temperature, the Prussian blue analog can maintain a relatively complete structure, and the metal ions (such as Fe 3+ or Co 3+ ) can remain in a relatively stable oxidation state. At this time, the catalytic performance of the Prussian blue analog is relatively excellent, which can well activate PMS to generate highly catalytic free radicals (such as SO4 •- ), thereby improving the catalytic efficiency. However, a higher sintering temperature can cause the crystal structure of the Prussian blue analog to be destroyed or restructured, and secondly, the high temperature can promote the migration or aggregation of metal ions, and even can cause the formation of certain metal oxides (such as Fe2O3, Fe3O4, etc.). These changes can reduce the activation ability of the catalytic ceramic membrane to oxidants such as PMS, resulting in a decrease in the catalytic effect.

[0040] In summary, the catalytic ceramic membranes of Example 1, Comparative Example 1 and Comparative Example 2 were selected for SEM detection, and the results are as follows: Figure 2 As shown, it can be observed that the catalytic ceramic membrane of Example 1 has more small pores, and the porous structure is more evenly distributed on the membrane surface.

[0041] Water permeability is one of the basic properties of ceramic membranes. High water permeability can reduce the actual use pressure of ceramic membranes and save operating costs. The present invention uses a peristaltic pump and a microbial reactor to conduct a filtration experiment. The prepared ceramic membrane is fixed inside the microbial reactor and filtered using a peristaltic pump. The flow rate of the peristaltic pump is 62.5L / m 2 The water permeability of Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 was tested respectively, and the test results are shown in the following table.

[0042] Table 2 Membrane water permeability

[0043] Examples Water permeability LMH / kPa Example 1 6.7 Example 2 6.9 Example 3 5.5 Comparative Example 1 6.1 Comparative Example 2 4.1

[0044] It can be seen that the water permeability of Comparative Example 1 is improved by 49% compared with Comparative Example 2, while that of Example 1 is improved by 63% compared with Comparative Example 2. That is, when calcined in air, PBA is more conducive to the formation of a porous structure of the membrane, which can increase the permeability to 1.63 times that of the alumina membrane. In addition, the Prussian blue-like content in Example 2 accounts for 25%. Although the water permeability of the prepared catalytic ceramic membrane is also improved with the increase of Prussian blue-like content, Example 2 is not the best choice based on economic benefits. The water permeability of the catalytic ceramic membrane sintered at 1100°C in Example 3 is reduced by 18% compared with that in Example 1 because the lower calcination temperature helps to maintain the structural integrity of the Prussian blue-like content, making its porosity higher and thus maintaining higher water permeability. However, higher temperatures may cause a certain degree of reconstruction of the crystal structure of the Prussian blue-like content or promote the occurrence of aggregation, making the Prussian blue-like lattice more compact, the pores may be reduced, and thus reduce water permeability. Based on the comprehensive considerations of economic efficiency and water permeability, it was determined that the catalytic ceramic membrane was prepared under the conditions required by Example 1.

[0045] The membrane has the dual functions of separation and catalysis. When applied to reactions, it can form a membrane-catalyzed reaction process that integrates catalysis and separation. The main principle is that as the reactants are generated, some or all of them pass through the membrane and leave the reaction zone. At the same time, due to the selective permeability of the catalytic ceramic membrane, the reactants remain in the reaction zone, causing the chemical equilibrium to continuously shift toward the product. Therefore, the present invention conducted catalytic performance tests on the catalytic ceramic membranes of Example 1 and Comparative Examples 1 and 2 using anionic dyes (AB9, edible brilliant blue solution). Catalytic tests were conducted in a peroxymonosulfate solution (PMS), where the AB9 concentration was 10 mg / L and the PMS concentration was 0.5 mM. The test results are shown in Figure 2. Figure 3 As shown in the figure, it can be seen that the catalytic efficiency of the catalytic ceramic membrane of Example 1 remains at about 95% from 10 minutes to 160 minutes, while that of the catalytic ceramic membrane of Comparative Example 1 is only about 65%, and there is almost no catalytic effect in Comparative Example 2. The low catalytic effect of Comparative Example 1 may be because the metal in the Prussian blue is easily oxidized during calcination in air, which may lead to an increase in the oxidation state of the metal (such as Fe 2+ Converted to Fe 3+ ), thereby enhancing its catalytic oxidation ability and effectively activating PMS. On the contrary, argon is an inert gas. Prussian blue calcined in argon is not easy to oxidize metals, and the oxidation state of the metal may remain at a low state. In this case, the catalytic activity of the catalytic ceramic membrane is relatively low because the metal ions with low oxidation states (such as Fe 2+ ) generally have a weaker ability to activate PMS. The above demonstrates that the catalytic ceramic membrane sintered in air, i.e., Example 1, can be well combined with PMS to degrade organic pollutants in situ on the ceramic membrane surface.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a high-throughput and high-efficiency catalytic ceramic membrane, characterized in that: The steps include: (1) Prussian blue-like powder and aluminum oxide powder are mixed uniformly in proportion to obtain a mixture, and the mixture is pressed at a pressure of 10 to 30 kPa for 3 to 7 minutes to obtain a dry film; the mass ratio of the Prussian blue-like powder to the aluminum oxide powder is 1:3 to 5; (2) sintering the dry blank in an air atmosphere at a temperature of 950-1100° C. for 5.5-6.5 hours to obtain the high-flux and high-efficiency catalytic ceramic membrane; The Prussian blue-like product is prepared by the following method: 1.2-3 g of Prussian blue powder and 1.5-2.5 g of cobalt chloride powder are dissolved in 50-200 ml of water at 25° C., stirred continuously for 24 hours, and centrifuged and dried to obtain the Prussian blue-like product.

2. The method for preparing a high-flux and high-efficiency catalytic ceramic membrane according to claim 1, characterized in that: The thickness of the dry blank is 2-4 mm.

3. A high-flux and high-efficiency catalytic ceramic membrane prepared by the method according to any one of claims 1-2.

4. Use of the high-flux and high-efficiency catalytic ceramic membrane according to claim 3 in water treatment.

5. The use according to claim 4, characterized in that The high-flux and high-efficiency catalytic ceramic membrane is used for peroxymonosulfate activation and oxidation of organic pollutants.

Images